Smile is a digital-only bank launched by the Co-op back in 1999, boasting "no queues, no hassle, no jargon, no nonsense".

But users appear to be crossing these claims off the list as they struggle to access their online banking and are directed to call centres they say aren't freephone numbers.

"Smile online banking unavailable this morning – long queues on phone lines, online chat told me they don't know when it will be available again... Time to switch to a more reliable service," wrote one customer on DownDetector.

The banks have admitted the fault, saying that they are investigating.

We're investigating the issue with our online banking and we are working to restore it as soon as possible 2/2

"I don't want to leave the bank ... but if I, like many others, cannot complete transactions online, then there will be no other choice. Sort it Coop.....before you end up with a bank...a call centre....and no customers," wrote another on DownDetector.

A Co-op Bank spokesperson told The Register: "We are currently experiencing an issue with our online banking which is affecting our customers' ability to log into their accounts through this channel. Our mobile banking app remains available to customers whilst we work to resolve the problem and customers can also contact us using the usual customer service telephone number. We hope to restore the online banking service as soon as possible and we apologise to our customers for any inconvenience caused/" ®